The state of Iowa allows married couples to separate their incomes on the income tax return. This allows each spouse to be taxed at their individual rate, not their joint on come rate. A big advantage when each has widely differing taxable income.
Itemized deductions are split as per the percentage established by the line 26 income ratio. The tax is then used at the level of each separate income.
An example, a spouse with a taxable income of $5000 will be taxed at that rate, not the rate of their joint income of $100K. Big break.